1. Field of the Invention
The present invention relates to a communication apparatus, a communication method, and a storage medium.
2. Description of the Related Art
In recent years, the robot technology and robot control technology have remarkably developed. Especially in a producing process, it is possible to correctly and continuously assemble small parts using a robot station (apparatus station) to which such robot technology is applied (Japanese Patent Laid-Open No. 2011-235398). There are two methods of arranging a robot station. As one of the two methods, one robot station performs a series of assembly processes by providing a plurality of hands with different functions to a robot so that the robot station performs various operations. As the other method, a plurality of robot stations are continuously arranged and used from an upstream process to a downstream process, and each robot station performs an assembling operation within a predetermined time (producing period) required for assembly.
On the other hand, there is an increasing demand for high-speed data communication for non-compressed moving image data and the like. In such situation, a millimeter-wave communication system using a wide frequency band of an unlicensed band has received attention, and the standards for millimeter-wave communication have been stipulated (IEEE802.15.3c-200, IEEE802.11ad). In millimeter-wave communication, it is possible to use a wide frequency band as an unlicensed band, thereby achieving high-speed transmission. In an assembly process in which the real-time characteristic is important, it is effective to transmit a radio signal within a robot station using millimeter-wave communication enabling high-speed transmission.
Furthermore, since millimeter-wave communication has a high carrier frequency and causes a large propagation loss according to a propagation distance, it is suitable for short-distance communication. If one robot station is used to perform one assembly process, a plurality of robot stations undergoing decentralized control are often arranged near the robot station. Alternatively, if a plurality of robot stations are used to perform an assembly process, it is desirably possible to readily change the number of robot stations to be used and their layout when the assembly process is changed or the like, and the plurality of robot stations individually undergo decentralized control and are designed so that their producing periods are almost equal to each other. By using millimeter-wave communication in each robot station, it becomes easy to perform an assembly process by decentralized control type robot stations each limited to communication within itself.
Even if one robot station performs one assembly process or a plurality of robot stations perform a series of assembly processes, each decentralized control type robot station manages its producing period. If each robot station incorporates a millimeter-wave communication system, communication within one robot station may interfere with that within an adjacent robot station although a millimeter-wave propagation distance is short. There is a problem that a robot station which is interfered with restarts next communication after completion of communication of a detected interference signal in order to avoid interference, thereby prolonging the producing period. Especially if a plurality of robot stations perform a series of assembly processes, the producing period of one robot station becomes longer due to interference of a signal, thereby causing a producing period deviation, and decreasing the production efficiency of an assembly line process as a whole.
Furthermore, if a plurality of robot stations perform a series of assembly processes, a clock period deviation occurs when the robot stations are stopped for control adjustment or modification of a drop of an attachment part or when each robot station operates according to a different clock, thereby reducing the production efficiency.
On the other hand, even if one robot station solely performs one assembly process, or a plurality of robot stations perform a series of assembly processes, each decentralized control type robot station manages its producing period. To optimize the production efficiency of a series of assembly processes as a whole, a robot station needs to detect and control the producing period of an adjacent robot station. It is, however, difficult for a conventional decentralized control type robot station to identify the producing period of an adjacent robot station. Furthermore, in a multi-cell environment in which a plurality of radio systems asynchronously operate at given periods, it is difficult to identify the producing period of an adjacent radio robot station.
Since the communication period of a radio system mounted on a robot station depends on the producing period of the robot station, it is possible to identify the producing period of the robot station by detecting the communication period of the mounted radio system. As a method of identifying the communication period of an adjacent communication system, a period and communication time are detected from a beacon of a different system (Japanese Patent No. 3849551). As described in Japanese Patent No. 3849551, a plurality of systems which operate at a period according to a predetermined protocol can capture communication of each other, thereby detecting the communication period. Like a radio system mounted on a robot station, however, it is difficult to detect a communication period when communication is performed at a period decided according to a protocol other than the predetermined communication protocol.